Example in the Use of Approved Documents
Problem:- the sizing of suspended upper floor joists to be spaced
at 400 mm centres with a clear span of 3„600 m for use
in a two storey domestic dwelling.
Building Regulation A1:- states that the building shall be constructed
so that the combined dead, imposed and wind loads are
sustained and transmitted by it to the ground †
(a) safely, and
(b) without causing such deflection or deformation of
any part of the building, or such movement of the
ground, as will impair the stability of any part of
another building.Approved Document A:- guidance on sizing floor joists can be
found in `Span Tables for Solid Timber Members in
Dwellings', published by the Timber Research And
Development Association (TRADA), and BS5268-2:
Structural use of timber. Code of practice for
permissible stress design, materials and workmanship.
Dead loading is therefore in the 0„25 to 0„50 kN/m^2 band
From table on page 633 suitable joist sizes are:- 38 ¾ 200, 50 ¾ 175,
(^63) ¾ 175 and 75¾ 150.
Final choice of section to be used will depend upon cost;
availability; practical considerations and/or personal preference.
Building Regulations---Applied